Any comments on this design? - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 12th October 2004, 01:36 PM   #1
icebear is offline icebear  Norway
diyAudio Member
 
Join Date: Dec 2003
Location: Aalesund
Default Any comments on this design?

Any opinions on this circuit. It's from diyparadise. I would go with triodeconnection on all the tubes. That will give like 5 wattt. Do anyone have experince with EL84 in SE vs PP ?


Bjorn
Attached Images
File Type: jpg el84pp.jpg (25.4 KB, 868 views)
  Reply With Quote
Old 12th October 2004, 01:49 PM   #2
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
By making the output stage double as the phase splitter, you lose some of the advantages of push-pull, most notably cancellation of second (and other even order) harmonic distortion. At the cost of efficiency, complication, and reliability, the CS will help mitigate this.

The logic behind this is questionable.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 12th October 2004, 04:27 PM   #3
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
On further review, I'm wrong about distortion. The CS does mitigate this. But I'm still right on inefficiency, heat, complication, and reliability.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 12th October 2004, 07:30 PM   #4
diyAudio Member
 
Sch3mat1c's Avatar
 
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
Well, it's always going to be as inefficient and unreliable because you've got class A there.

It'll work fine as long as gain is enough... it should take twice the signal drive as normal PP, I think.

Tim
__________________
Seven Transistor Labs
Projects and Resources
  Reply With Quote
Old 13th October 2004, 07:56 AM   #5
Account Disabled
 
Join Date: Sep 2004
Location: Earth
A nice two stages P-P amp!
Go with an UL tranny, so you can hear it triode ,pentode and UL!Also try it with G2 ( screen ) something lower than 300V, say 200-250V.Just for an experiment.Some people like it better than pentode or UL.
Also try it without 470u.I thing this cap doesn't belong there.Read at diyparadise the original article about this amp.There's a reference about this cap that I don't remember.
  Reply With Quote
Old 16th May 2009, 08:17 PM   #6
Klimon is offline Klimon  Belgium
diyAudio Member
 
Join Date: Apr 2005
Location: Leuven
Quote:
it should take twice the signal drive as normal PP
Is this correct?

Thanks!

Simon
  Reply With Quote
Old 16th May 2009, 08:32 PM   #7
diyAudio Member
 
Join Date: May 2007
It is correct, you loose 6dB. But his how all LTP, long tail phase inverters work.

But I would do a "Schade" on the output EL84s and choose another driver like 6C45 or 6H30.
  Reply With Quote
Old 16th May 2009, 09:32 PM   #8
JohanB is offline JohanB  Sweden
diyAudio Member
 
Join Date: May 2009
Location: Stockholm
Electronic World published this circuit in 1961 with a 6C4 as input driver tube. This was before the time of low voltage ccs's, so there is just a resistor in the cathodes.
You can actually see this as a single ended amplifier (V2) with a opt current equalizing tube (V3) and active load. Ofcourse the amplitude on V3 anode will be lower than on V2, but the circuit vill cancel a lot of distorsion anyway. The second harmonic of the 6C4 is also in opposite phase to that in V2.
I think this circuit could also be tried with 6CW5/EL86's as output tubes, in triode or pentode operation, with even better performance than the 6BQ5/EL84. For a budget project, the low priced NOS 15CW5/PL84 are plentiful. same specs as 6CW5/EL86 despite the number PL84!! The only difference is that it takes 15V at 300mA for the heater.


http://triodeel.com/compact.html

JohanB
  Reply With Quote
Old 16th May 2009, 11:41 PM   #9
JohanB is offline JohanB  Sweden
diyAudio Member
 
Join Date: May 2009
Location: Stockholm
I sew that this first circuit in diyparadise with CCs was revised by someone later on, back to a common resistor in the cathodes (as in the original Leibowitz circuit). See link below.

http://diyparadise.com/web/index.php...d=58&Itemid=26

I'm still puzzled about using power tubes (6BQ5 or later 1/2 5687) for driving the grid of the output tube. I think it's an overkill (and expensive) to use as driver, especially in pentode and UL-mode.

If not using a 6C4 (EC90) in the pentode mode operation, 1/2 12AT7/ECC81 (EC92/6AB4) will have enough gain and power also for the millercaps in triode mode. Will also give a nice 2:nd harmonic to partly cancel the resulting 2:nd harmonic in the first output tube.


JohanB
  Reply With Quote
Old 17th May 2009, 03:42 AM   #10
diyAudio Member
 
Join Date: Oct 2004
Location: Maui, Hawai'i, USA
I have two thoughts on this setup:

Yes, singly driving a diff-amp with a long tail causes the cathode of the driven tube to follow the grid halfway, so we're dividing the gain of the driver tube between the two outputs tubes.  An EL84 in the 'first hole', as shown is not gonna get you there without a truly monster signal coming in the front - much greater than line level.  A bigger gain low rp tube like the 6GK5 or similar would ameliorate this problem.

The CCS in the output tail does solve the horrendous output signal imbalance problem of the original Compact, but I don't know how thick on the ground CCS circuits are that can stay firmly in regulation at 80mA with only the 18v (or so) cathode lift of the EL84 outputs across them.  Maybe somebody else here, like Stuart, can comment on this.  If it don't fly, we could always build a little 50v or so negative supply for the tail.

Otherwise, why not try it? All the parts could be recycled if it doesn't sound good.

Aloha,

Poinz
AudioTropic
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Need comments on amp design mightydub Solid State 28 24th December 2008 02:01 AM
My first amp design - comments blueskynis Solid State 36 26th March 2008 04:38 PM
need comments on amp design metebalci Tubes / Valves 0 10th September 2006 09:03 PM
comments on this design.. GeirW Tubes / Valves 6 13th February 2004 09:24 AM
Comments on this design? G Tubes / Valves 0 16th October 2003 06:09 PM


New To Site? Need Help?

All times are GMT. The time now is 06:07 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2